The galvanized body of the car is a reliable protection against corrosion, which keeps the metal intact for decades. However, even the most persistent zinc layer wears out over time, chips, scratches and rust foci appear, requiring immediate intervention. Owners often wonder if it is possible to restore the protective coating on their own and how to paint the galvanizing so that the new layer holds as tightly as the factory one.
The process of galvanized surface painting is radically different from working with conventional steel or aluminum. The main difficulty lies in the chemical inertness of zinc: standard soils and enamel simply cannot catch on a smooth, greasy and slippery surface. If you ignore the specifics of the material, the paint will rise in bubbles after a few months, opening the metal to moisture. Therefore proper preparation The choice of specialized materials plays a role here.
In this article, we will analyze all the stages of work: from assessing the condition of the old coating to finishing polishing. You will learn what types of soils exist for zinc, why you can not use conventional acid compounds and how to achieve factory quality in garage conditions. Compliance with the technology will allow you not only to paint the defect, but to fully restore the anticorrosion protection of the body.
Features of zinc coating and choice of materials
Zinc is applied to the body panels by hot galvanizing, electroplating or spraying. In any case, the thinnest oxide film is formed on the surface, which prevents rusting. The problem is that this film has low adhesion to most paints (varnishes). Ordinary acrylic or alkyd soil, lying on zinc, does not penetrate into the pores, but creates a separate layer, which eventually peels off under the influence of vibration and temperature changes.
There are special galvanizing procedures for working with galvanizing archetypalThey are often called primers. They contain active components that react chemically with zinc oxides, creating a strong bond. Also popular are epoxy soils, which create a mechanical lock due to high density and penetrating ability. It is important to understand that the use of acid (phosphate) soils on pure zinc forbiddenSince the acid can destroy the protective layer of the metal, causing a back reaction.
When choosing materials, pay attention to the labeling "for galvanized surfaces" or "Zinc". Modern two-component systems on an epoxy basis are considered the gold standard in body repair. They provide not only adhesion, but also additional electrochemical protection, working as a sacrificial anode paired with the base metal.
⚠️ Warning: Never apply nitroemali or conventional alkyd paints directly to zinc without soil. The solvents contained in them can react with the metal, which will lead to instantaneous swelling of the coating and the appearance of "craters".
Tools and workplace preparation
The quality of painting is 80% dependent on preparation. You will need not only a spray gun and compressor, but also a whole arsenal of hand tools. For cleaning galvanizing, you can not use coarse abrasives, which can leave deep furrows that have become centers of future corrosion. The best choice will be grinding wheels with a gradation of P240-P400 for primary processing and P600-P800 for finishing.
It is necessary to have a high-quality degreasing liquid. Zinc surfaces are often covered with factory conservation oils or transport lubricants that are not visible to the eye but fatal for adhesion. Use special silicone removers or proven antisilicones. Also prepare paint tape, cover film and, of course, personal protective equipment: a respirator with carbon filters and gloves.
The workplace should be clean, dry and well lit. Dust is the painter's main enemy. If you work in a garage, be sure to do a wet cleaning an hour before the work starts to settle the suspension. The room temperature should be in accordance with the recommendations of the materials manufacturer, usually from +18 ° C to +25 ° C.
Use a tack cloth immediately before applying the soil. It removes the smallest dust that the air purge did not take, providing a perfectly smooth surface.
Technology of surface preparation for painting
The first step is always a thorough washing and degreasing of the repair area. Even if the damage seems small, you need to treat the area with a margin of 10-15 cm around the defect. After washing, the surface is wiped with antisilicone twice: the first wipe is washed away the contamination, the second (dry) is wiped dry. This is a basic step, without which paint-painting Impossible.
Then comes the mechanical treatment. If there are galvanizing swelling or old paint, they must be removed to metal. The galvanized layer is characterized by the fact that it does not rust as quickly as black steel, but when damaged, zinc begins to break down, forming a white coating of oxides. These areas need to be cleaned to shiny metal. Use a grinder or manually a P320 abrasive, trying not to overheat the metal so as not to deform the thin sheet.
After mechanical cleaning, the surface is degreased again. It is important to check the result with the "white napkin method": run a clean white rag on the metal. If there are traces of fat or dirt on it, the procedure is repeated. Only a perfectly clean surface is ready for the primer.
☑️ Checklist of preparations
Application of adhesive soil (Primer)
Grounding is the most responsible stage. For galvanizing, we use a special one-component adhesive soil (primer). It is applied in a thin, almost transparent layer ("fog"). The main task of this layer is not to create a thick film, but to chemically bind to zinc. It should be applied quickly, avoiding drying out, since many primers are active for a limited time.
The application technology requires accurate adjustment of the spray gun. The pressure is usually 2-3 atmospheres, the torch is medium. The distance from the nozzle to the detail is 15-20 cm. Movements should be smooth and uniform. After applying the first layer, you need to give time for the solvent to evaporate (Flash-off time), usually 5-10 minutes at room temperature. At this time, the layer becomes matte.
If you use two-component epoxy soil as an alternative, the technology changes. Epoxy is applied with a wet, full-fledged layer, as it performs the function of an insulator and leveler. However, an adhesive primer is often recommended to be applied over epoxy soil for maximum reliability, especially if it is a high vibration or humidity zone.
⚠️ Warning: Do not attempt to speed up the drying of the primer with a building hair dryer or heat gun. Dramatic heating can "boil" the solvent inside a thin film, creating microbubbles that disrupt the adhesion of the next layer.
Secrets of the professionals
Many masters use the wet-wet method for primer and ground, if the products of one line allow it. This saves time on grinding, but requires high qualification to prevent leaks.
Primary soil application and leveling
After the adhesive layer has dried (usually it takes from 30 minutes to several hours, read the instructions on the jar!), you can move to the main soil. Most often, acrylic two-component soil-filler is used. It hides the risks from grinding and minor irregularities. It is applied in 2-3 layers with interlayer drying for 10-15 minutes.
It is important not to overdo it with thickness. Too thick a layer of soil can lead to shrinkage when drying or, conversely, to a long drying, which in the future will cause problems with paint. After complete polymerization (usually 12-24 hours), the soil is polished. For galvanizing, which often has complex geometry, it is important not to wipe the soil to metal so as not to disturb the protection.
Grinding is carried out with abrasive P400-P500 under painting with acrylic or P600-P800 under metallic. If after grinding risks or holes were found, the process of priming is repeated locally. Ideally prepared surface should be smooth to the touch, without changes and steps.
Painting and finishing
The final stage is the application of the basic enamel. The color is selected by the body code, but it falls on galvanizing in the same way as on any other soil, if the primer technology is observed. The base is applied in 2-3 layers, controlling the overlap and shade. Between the layers, pause for evaporation of the solvent (10-15 minutes).
After drying the base (usually 20-30 minutes), varnish is applied. For cars operated in harsh conditions, it is recommended to use 2K-varnishes of increased strength (HS - High Solid). Lacquer is applied in 2 layers: the first thin "ghost", the second - a full wet layer for gloss.
After drying completely (from 24 hours to a week for a gain of strength), the surface can be polished. Polishing removes the "shagrin" (orange peel) and gives a deep shine. For galvanized parts, which are often in the lower part of the body (thresholds, arches), polishing can be excessive, the main thing is the tightness of the coating.
The quality of the final result depends on the drying time between the layers. Do not rush to apply varnish to an undried base - this will lead to clouding and loss of shine.
Comparison of galvanizing materials
Choosing the right soil is half of the success. There are many products on the market, but not all of them are suitable for working with zinc. Below is a comparative table of the main types of soil used in body repairs.
| Type of soil | Adhesion to zinc | Anti-corrosion | Difficulty of application |
|---|---|---|---|
| Acid (phosphate) | Bad/Aggressive | Tall. | Low. |
| Epoxy (2K) | Good (mechanical) | Very high. | Medium |
| Adhesive primer | Excellent (chemical) | Medium | Tall. |
| Acrylic filler | Demands a primer. | Low. | Low. |
As you can see from the table, the ideal option is a combination: an adhesive primer for clutch + epoxy soil for protection + acrylic filler for alignment. Only one type of soil is possible, but it is compromised in quality.
⚠️ Warning: When working with two-component materials (epoxy, acrylic, varnish), always use a respirator with organic filters. The isocyanate vapors contained in hardeners are odorless, but extremely toxic and can cause severe lung damage.
Frequently Asked Questions (FAQ)
Can I paint the galvanizing with a regular spray paint?
Technically possible, but the result will be short-lived. Conventional aerosols do not contain zinc adhesives. Without the preliminary application of a special primer, such paint will begin to peel off after one or two seasons. For high-quality repairs, use the system: primer for galvanizing + soil-filler + enamel.
Should I completely clean the old zinc to shiny metal?
No, it is not necessary to completely clean zinc and even harmful. Zinc is protection. Clean only damaged areas where the metal has already oxidized or swelled. If the old zinc layer is held firmly, has no cracks and detachments, it is enough to simply wrap (remove gloss) with abrasive P400-P600 and degrease.
How long can you use the car after painting?
Departure on the road is possible 24 hours after applying the varnish, when the coating will gain primary hardness. However, the full chemical resistance and hardness of the paint coating is gaining within 7-14 days. During this period, it is not recommended to wash the car with active chemistry, use high-pressure washers or polish the body.
Why can’t you use acid soil on galvanizing?
Acid (phosphate) soils contain orthophosphoric acid, which is designed to convert iron oxides (rust) into stable compounds. On zinc, the acid reacts, destroying the protective oxide layer and the metal itself, which leads to loss of anticorrosion properties and poor adhesion of subsequent layers.